Conventionally, when an abnormality occurs in tire air pressure during running of a vehicle, this may cause an accident; there have thus been developed devices automatically monitoring the tire air pressure to raise an alarm when an abnormality occurs in the tire air pressure. For example, a device disclosed in Japanese Patent Publication No. 2003-121281 (Patent Document 1) includes a wheel for mounting a tire, a tire pressure sensing unit and a display unit. The tire pressure sensing unit is arranged in a sensing unit housing slot formed at a predetermined position of a corresponding surface abutting on a tubeless tire of a wheel. Information obtained by sensing a tire pressure is outputted to the display unit as a signal, and the display unit displays the information on tire pressure.
When this device is used, the driver can perceive an abnormal phenomenon such as decrease or increase of the tire pressure at any time before running or during running and early perform a tire inspection or emergency measure.
Further, an abnormality monitoring device for a pneumatic tire disclosed in Japanese Patent Publication No. 2002-103931 (Patent Document 2) includes: a temperature sensing and transmitting unit arranged in a tire air chamber for sensing a temperature in the tire air chamber and transmitting by wireless the sensed temperature information to the outside of the tire; and a burst occurrence prediction unit arranged outside the tire for applying an arithmetic processing to the temperature information and raising an alarm when an abnormality is detected. The burst occurrence prediction unit includes a receiving device receiving the temperature information transmitted from the temperature sensing and transmitting unit, a memory section accumulating the temperature information as time sequence data at a predetermined time interval, a filter section for eliminating abnormal data from the time sequence data, a comparison calculation section comparing a difference between data of plural tires and a difference between change ratios thereof and comparing those with standard values to transmit abnormality information when an abnormality is detected, and an alarm transmitting section receiving the abnormality information and raising a burst alarm.
While this device is comparatively simple, the air chamber internal temperature of each tire can be accurately grasped to thereby predict appropriately an occurrence of burst.
Also, when the brake of the tire is abnormally heated, this may lower the braking force, causing an accident; there have thus been developed devices automatically monitoring a temperature of a tire brake and raising an alarm when an abnormality occurs in brake temperature. For example, a brake heating alarming device disclosed in Japanese Patent Publication No. 10-44976 (Patent Document 3) includes a temperature sensor measuring a temperature of a tire brake, a unit comparing a difference between the brake temperature measured by the temperature sensor and the brake temperature measured after the lapse of a given time relative to the precedent measurement with a preliminarily set value, and a unit raising an alarm in response to the comparison result.
According to this device, the driver can be notified about brake heating caused by an excessive use of the brake, and the braking force can thus be prevented from lowering and also, the brake parts can be prevented from wearing out.
Patent Document 1: Japanese Patent Publication No. 2003-121281
Patent Document 2: Japanese Patent Publication No. 2002-103931
Patent Document 3: Japanese Patent Publication No. 10-44976
Generally, in a leading drum brake used often in trucks or buses, if adjustment is erroneously made, even when the brake is not activated, the brake shoe is opened due to self servo effect that the brake has in principle, thus generating frictional heat.
More specifically, as illustrated in FIG. 26, a drum brake 1 includes a wheel cylinder 12 secured to a back plate 11, connecting rods 13a and 13b, an adjuster bolt 13c, a parking brake lever 14, brake springs 15a and 15b, an adjuster spring 15c, an adjuster lever 16, brake shoes 17A and 17B, and a brake drum 18. The brake shoes 17A and 17B having applied thereto a frictional material called a lining (not illustrated) are pressed against the inner side of the brake drum 18 rotating along with the vehicle tire/wheel, and frictional effect caused by this allows deceleration.
Also, the major characteristic of the drum brake is its self servo effect (self boosting effect); that is, when the brake shoes 17A and 17B are pressed against the rotating brake drum 18, force biting into (force pulled into) the brake drum 18 is generated, whereby the brake drum 18 is pressed by stronger force, thus generating stronger braking force.
However, if adjustment of a gap between the brake shoes 17A and 17B and the brake drum 18 is erroneously made using the adjuster bolt 13c and the adjuster lever 16, even when the brake is not activated, the brake shoes 17A and 17B are opened due to the self servo effect and dragged by the brake drum 18, generating frictional heat.
Also, in bearings used in an axle bearing mechanism, when grease filling amount or pressurization is erroneously applied, frictional resistance associated with rotation increases, thus raising temperature.
These phenomena not only increase running resistance of the vehicle, resulting in low mileage, but also raise the temperature of the tire made from rubber being a material easily affected by heat, leading to a burst of the tire at worst.
Similarly to the drum brake described above, in a disk brake, also, maladjustment may cause heating. More specifically, regarding a disk brake device, when it comes to a vehicle provided with Anti Lock Brake System (ABS) proliferating rapidly in recent years, the upper threshold of regular liquid pressure is raised due to mounting of a liquid pressure booster; thus when liquid pressure is lowered in a region exceeding a conventional regular liquid pressure, since piston return amount is insufficient, the pad contacts the brake disk during rotating at the time of non-braking, causing a phenomenon of dragging the pad. Frictional heat is generated by such pad dragging.
The present invention addresses the above problem, with the object of providing a vehicle abnormality detection method for detecting an abnormality in which a high temperature is generated due to maladjustment of a vehicle axle bearing mechanism section or vehicle brake mechanism section, and a device thereof and a sensor unit thereof.